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| 1 | +#include "MS5837.h" |
| 2 | +#include <Wire.h> |
| 3 | + |
| 4 | +const uint8_t MS5837_ADDR = 0x76; |
| 5 | +const uint8_t MS5837_RESET = 0x1E; |
| 6 | +const uint8_t MS5837_ADC_READ = 0x00; |
| 7 | +const uint8_t MS5837_PROM_READ = 0xA0; |
| 8 | +const uint8_t MS5837_CONVERT_D1_8192 = 0x4A; |
| 9 | +const uint8_t MS5837_CONVERT_D2_8192 = 0x5A; |
| 10 | + |
| 11 | +const float MS5837::Pa = 100.0f; |
| 12 | +const float MS5837::bar = 0.001f; |
| 13 | +const float MS5837::mbar = 1.0f; |
| 14 | + |
| 15 | +const uint8_t MS5837::MS5837_30BA = 0; |
| 16 | +const uint8_t MS5837::MS5837_02BA = 1; |
| 17 | +const uint8_t MS5837::MS5837_UNRECOGNISED = 255; |
| 18 | + |
| 19 | +const uint8_t MS5837_02BA01 = 0x00; // Sensor version: From MS5837_02BA datasheet Version PROM Word 0 |
| 20 | +const uint8_t MS5837_02BA21 = 0x15; // Sensor version: From MS5837_02BA datasheet Version PROM Word 0 |
| 21 | +const uint8_t MS5837_30BA26 = 0x1A; // Sensor version: From MS5837_30BA datasheet Version PROM Word 0 |
| 22 | + |
| 23 | +MS5837::MS5837() { |
| 24 | + fluidDensity = 1029; |
| 25 | +} |
| 26 | + |
| 27 | +bool MS5837::begin(TwoWire &wirePort) { |
| 28 | + return (init(wirePort)); |
| 29 | +} |
| 30 | + |
| 31 | +bool MS5837::init(TwoWire &wirePort) { |
| 32 | + _i2cPort = &wirePort; //Grab which port the user wants us to use |
| 33 | + |
| 34 | + // Reset the MS5837, per datasheet |
| 35 | + _i2cPort->beginTransmission(MS5837_ADDR); |
| 36 | + _i2cPort->write(MS5837_RESET); |
| 37 | + _i2cPort->endTransmission(); |
| 38 | + |
| 39 | + // Wait for reset to complete |
| 40 | + delay(10); |
| 41 | + |
| 42 | + // Read calibration values and CRC |
| 43 | + for ( uint8_t i = 0 ; i < 7 ; i++ ) { |
| 44 | + _i2cPort->beginTransmission(MS5837_ADDR); |
| 45 | + _i2cPort->write(MS5837_PROM_READ+i*2); |
| 46 | + _i2cPort->endTransmission(); |
| 47 | + |
| 48 | + _i2cPort->requestFrom(MS5837_ADDR,2); |
| 49 | + C[i] = (_i2cPort->read() << 8) | _i2cPort->read(); |
| 50 | + } |
| 51 | + |
| 52 | + // Verify that data is correct with CRC |
| 53 | + uint8_t crcRead = C[0] >> 12; |
| 54 | + uint8_t crcCalculated = crc4(C); |
| 55 | + |
| 56 | + if ( crcCalculated != crcRead ) { |
| 57 | + return false; // CRC fail |
| 58 | + } |
| 59 | + |
| 60 | + uint8_t version = (C[0] >> 5) & 0x7F; // Extract the sensor version from PROM Word 0 |
| 61 | + |
| 62 | + // Set _model according to the sensor version |
| 63 | + if (version == MS5837_02BA01) |
| 64 | + { |
| 65 | + _model = MS5837_02BA; |
| 66 | + } |
| 67 | + else if (version == MS5837_02BA21) |
| 68 | + { |
| 69 | + _model = MS5837_02BA; |
| 70 | + } |
| 71 | + else if (version == MS5837_30BA26) |
| 72 | + { |
| 73 | + _model = MS5837_30BA; |
| 74 | + } |
| 75 | + else |
| 76 | + { |
| 77 | + _model = MS5837_UNRECOGNISED; |
| 78 | + } |
| 79 | + // The sensor has passed the CRC check, so we should return true even if |
| 80 | + // the sensor version is unrecognised. |
| 81 | + // (The MS5637 has the same address as the MS5837 and will also pass the CRC check) |
| 82 | + // (but will hopefully be unrecognised.) |
| 83 | + return true; |
| 84 | +} |
| 85 | + |
| 86 | +void MS5837::setModel(uint8_t model) { |
| 87 | + _model = model; |
| 88 | +} |
| 89 | + |
| 90 | +uint8_t MS5837::getModel() { |
| 91 | + return (_model); |
| 92 | +} |
| 93 | + |
| 94 | +void MS5837::setFluidDensity(float density) { |
| 95 | + fluidDensity = density; |
| 96 | +} |
| 97 | + |
| 98 | +void MS5837::read() { |
| 99 | + //Check that _i2cPort is not NULL (i.e. has the user forgoten to call .init or .begin?) |
| 100 | + if (_i2cPort == NULL) |
| 101 | + { |
| 102 | + return; |
| 103 | + } |
| 104 | + |
| 105 | + // Request D1 conversion |
| 106 | + _i2cPort->beginTransmission(MS5837_ADDR); |
| 107 | + _i2cPort->write(MS5837_CONVERT_D1_8192); |
| 108 | + _i2cPort->endTransmission(); |
| 109 | + |
| 110 | + delay(20); // Max conversion time per datasheet |
| 111 | + |
| 112 | + _i2cPort->beginTransmission(MS5837_ADDR); |
| 113 | + _i2cPort->write(MS5837_ADC_READ); |
| 114 | + _i2cPort->endTransmission(); |
| 115 | + |
| 116 | + _i2cPort->requestFrom(MS5837_ADDR,3); |
| 117 | + D1_pres = 0; |
| 118 | + D1_pres = _i2cPort->read(); |
| 119 | + D1_pres = (D1_pres << 8) | _i2cPort->read(); |
| 120 | + D1_pres = (D1_pres << 8) | _i2cPort->read(); |
| 121 | + |
| 122 | + // Request D2 conversion |
| 123 | + _i2cPort->beginTransmission(MS5837_ADDR); |
| 124 | + _i2cPort->write(MS5837_CONVERT_D2_8192); |
| 125 | + _i2cPort->endTransmission(); |
| 126 | + |
| 127 | + delay(20); // Max conversion time per datasheet |
| 128 | + |
| 129 | + _i2cPort->beginTransmission(MS5837_ADDR); |
| 130 | + _i2cPort->write(MS5837_ADC_READ); |
| 131 | + _i2cPort->endTransmission(); |
| 132 | + |
| 133 | + _i2cPort->requestFrom(MS5837_ADDR,3); |
| 134 | + D2_temp = 0; |
| 135 | + D2_temp = _i2cPort->read(); |
| 136 | + D2_temp = (D2_temp << 8) | _i2cPort->read(); |
| 137 | + D2_temp = (D2_temp << 8) | _i2cPort->read(); |
| 138 | + |
| 139 | + calculate(); |
| 140 | +} |
| 141 | + |
| 142 | +void MS5837::calculate() { |
| 143 | + // Given C1-C6 and D1, D2, calculated TEMP and P |
| 144 | + // Do conversion first and then second order temp compensation |
| 145 | + |
| 146 | + int32_t dT = 0; |
| 147 | + int64_t SENS = 0; |
| 148 | + int64_t OFF = 0; |
| 149 | + int32_t SENSi = 0; |
| 150 | + int32_t OFFi = 0; |
| 151 | + int32_t Ti = 0; |
| 152 | + int64_t OFF2 = 0; |
| 153 | + int64_t SENS2 = 0; |
| 154 | + |
| 155 | + // Terms called |
| 156 | + dT = D2_temp-uint32_t(C[5])*256l; |
| 157 | + if ( _model == MS5837_02BA ) { |
| 158 | + SENS = int64_t(C[1])*65536l+(int64_t(C[3])*dT)/128l; |
| 159 | + OFF = int64_t(C[2])*131072l+(int64_t(C[4])*dT)/64l; |
| 160 | + P = (D1_pres*SENS/(2097152l)-OFF)/(32768l); |
| 161 | + } else { |
| 162 | + SENS = int64_t(C[1])*32768l+(int64_t(C[3])*dT)/256l; |
| 163 | + OFF = int64_t(C[2])*65536l+(int64_t(C[4])*dT)/128l; |
| 164 | + P = (D1_pres*SENS/(2097152l)-OFF)/(8192l); |
| 165 | + } |
| 166 | + |
| 167 | + // Temp conversion |
| 168 | + TEMP = 2000l+int64_t(dT)*C[6]/8388608LL; |
| 169 | + |
| 170 | + //Second order compensation |
| 171 | + if ( _model == MS5837_02BA ) { |
| 172 | + if((TEMP/100)<20){ //Low temp |
| 173 | + Ti = (11*int64_t(dT)*int64_t(dT))/(34359738368LL); |
| 174 | + OFFi = (31*(TEMP-2000)*(TEMP-2000))/8; |
| 175 | + SENSi = (63*(TEMP-2000)*(TEMP-2000))/32; |
| 176 | + } |
| 177 | + } else { |
| 178 | + if((TEMP/100)<20){ //Low temp |
| 179 | + Ti = (3*int64_t(dT)*int64_t(dT))/(8589934592LL); |
| 180 | + OFFi = (3*(TEMP-2000)*(TEMP-2000))/2; |
| 181 | + SENSi = (5*(TEMP-2000)*(TEMP-2000))/8; |
| 182 | + if((TEMP/100)<-15){ //Very low temp |
| 183 | + OFFi = OFFi+7*(TEMP+1500l)*(TEMP+1500l); |
| 184 | + SENSi = SENSi+4*(TEMP+1500l)*(TEMP+1500l); |
| 185 | + } |
| 186 | + } |
| 187 | + else if((TEMP/100)>=20){ //High temp |
| 188 | + Ti = 2*(dT*dT)/(137438953472LL); |
| 189 | + OFFi = (1*(TEMP-2000)*(TEMP-2000))/16; |
| 190 | + SENSi = 0; |
| 191 | + } |
| 192 | + } |
| 193 | + |
| 194 | + OFF2 = OFF-OFFi; //Calculate pressure and temp second order |
| 195 | + SENS2 = SENS-SENSi; |
| 196 | + |
| 197 | + TEMP = (TEMP-Ti); |
| 198 | + |
| 199 | + if ( _model == MS5837_02BA ) { |
| 200 | + P = (((D1_pres*SENS2)/2097152l-OFF2)/32768l); |
| 201 | + } else { |
| 202 | + P = (((D1_pres*SENS2)/2097152l-OFF2)/8192l); |
| 203 | + } |
| 204 | +} |
| 205 | + |
| 206 | +float MS5837::pressure(float conversion) { |
| 207 | + if ( _model == MS5837_02BA ) { |
| 208 | + return P*conversion/100.0f; |
| 209 | + } |
| 210 | + else { |
| 211 | + return P*conversion/10.0f; |
| 212 | + } |
| 213 | +} |
| 214 | + |
| 215 | +float MS5837::temperature() { |
| 216 | + return TEMP/100.0f; |
| 217 | +} |
| 218 | + |
| 219 | +// The pressure sensor measures absolute pressure, so it will measure the atmospheric pressure + water pressure |
| 220 | +// We subtract the atmospheric pressure to calculate the depth with only the water pressure |
| 221 | +// The average atmospheric pressure of 101300 pascal is used for the calcuation, but atmospheric pressure varies |
| 222 | +// If the atmospheric pressure is not 101300 at the time of reading, the depth reported will be offset |
| 223 | +// In order to calculate the correct depth, the actual atmospheric pressure should be measured once in air, and |
| 224 | +// that value should subtracted for subsequent depth calculations. |
| 225 | +float MS5837::depth() { |
| 226 | + return (pressure(MS5837::Pa)-101300)/(fluidDensity*9.80665); |
| 227 | +} |
| 228 | + |
| 229 | +float MS5837::altitude() { |
| 230 | + return (1-pow((pressure()/1013.25),.190284))*145366.45*.3048; |
| 231 | +} |
| 232 | + |
| 233 | + |
| 234 | +uint8_t MS5837::crc4(uint16_t n_prom[]) { |
| 235 | + uint16_t n_rem = 0; |
| 236 | + |
| 237 | + n_prom[0] = ((n_prom[0]) & 0x0FFF); |
| 238 | + n_prom[7] = 0; |
| 239 | + |
| 240 | + for ( uint8_t i = 0 ; i < 16; i++ ) { |
| 241 | + if ( i%2 == 1 ) { |
| 242 | + n_rem ^= (uint16_t)((n_prom[i>>1]) & 0x00FF); |
| 243 | + } else { |
| 244 | + n_rem ^= (uint16_t)(n_prom[i>>1] >> 8); |
| 245 | + } |
| 246 | + for ( uint8_t n_bit = 8 ; n_bit > 0 ; n_bit-- ) { |
| 247 | + if ( n_rem & 0x8000 ) { |
| 248 | + n_rem = (n_rem << 1) ^ 0x3000; |
| 249 | + } else { |
| 250 | + n_rem = (n_rem << 1); |
| 251 | + } |
| 252 | + } |
| 253 | + } |
| 254 | + |
| 255 | + n_rem = ((n_rem >> 12) & 0x000F); |
| 256 | + |
| 257 | + return n_rem ^ 0x00; |
| 258 | +} |
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